A rectangular drawing of a plane graph G is a drawing of G such that each vertex is drawn as a point, each edge is drawn as a horizontal or a vertical line segment, and the contour of each face is drawn as a rectangle. A necessary and sufficient condition for the existence of a rectangular drawing has been known only for the case where exactly four vertices of degree 2 are designated as corners...

The previously unknown crystal structure of barium perchlorate anhydrate, determined and refined from laboratory X-ray powder diffraction data, represents a new structure type. The title compound was obtained by heating hydrated barium perchlorate [Ba(ClO4)2·xH2O] at 423 K in vacuo for 6 h. It crystallizes in the ortho-rhom-bic space group Fddd. The asymmetric unit contains one Ba (site symmetr...

Objectives: The aims of this study were to test whether lightening of the overexposed radiographs improve determination of endodontic files length and whether lightened radiographs are comparable with ideally exposed radiographs. Material and Methods: Four dried human skull coated with soft tissue-equivalent wax used for exposing radiographs of the upper molars. First, the endodontic file was p...

The role of environmental geometry in maintaining spatial orientation was measured in immersive virtual reality using a spatial updating task (requiring maintenance of orientation during locomotion) within rooms varying in rotational symmetry (the number of room orientations providing the same perspective). Spatial updating was equally good in trapezoidal, rectangular and square rooms (one-fold...

In this paper, a new method is presented for encryption of colored images. This method is based on using stack data structure and chaos which make the image encryption algorithm more efficient and robust. In the proposed algorithm, a series of data whose range is between 0 and 3 is generated using chaotic logistic system. Then, the original image is divided into four subimages, and these four i...

As an analytical type of approach, Critical Discourse Analysis (CDA) deals with the emphasis on social practice, identity, power, and ideology built through text and speech in socio-political and educational contexts. Having proposed a theoretical framework, it uncovered all discrepant ways through which power and societal practices are produced in written and spoken texts. Moreover, mingled wi...